DIVERSITY, RELATIVE ABUNDANCE AND BIOLOGY OF FISHES IN BELES AND GILGEL BELES RIVERS, ABAY BASIN, ETHIOPIA A thesis presented to the School of Graduate Studies, Addis Ababa University, In partial fulfillment of the requirements for the Degree of Master of Science in Biology (Fishery and Aquatic Sciences) By ZELEKE BERIE FEBRUARY 2007 ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES DIVERSITY, RELATIVE ABUNDANCE AND BIOLOGY OF FISHES IN BELES AND GILGEL BELES RIVERS, ABAY BASIN, ETHIOPIA By ZELEKE BERIE Approved by the Examining Board: Name Signature Dr. Abebe Getahun………………………………………… ……………… Research Advisor Dr. Demeke Admassu………………………………………. .......................... Examiner DR. Seyoum Mengistou…………………………………… ……………… Chairman, Department Graduate Committee DECLARATION The thesis is my original work, has not been presented for a degree in any other University and that all of the materials used for the thesis have been duly acknowledged. Name: Zeleke Berie Signature: ________ Date of submission: ________ This work has been presented with my approval as supervisor. Name: Abebe Getahun (PhD) Signature: ________ Date: ________ Financial support was provided by Graduate and Research Program of Addis Ababa University, Systematic Research Fund of American Museum of Natural History and Development Innovation Fund of the Zoological Natural History Museum, AAU through Dr. Abebe Getahun. Almost all logistic necessities for fieldwork were provided by Amhara Regional Agricultural Research Institute (ARARI) through its Bahir Dar FOALRC. Finally and most importantly, endless thanks to my wife Mulugojam Mekuriaw and My children, Rufahil, Eyobial and Bereket, who are the sole source of motivation and encouragement, and they are highly appreciated for their patience in my absence for so long a time. I praise my LORD. II TABLE OF CONTENTS Page Acknowledgements…………………………………………………...…........…...…I List of Tables………………………………………………………...…...……........V List of Figures……………………………………………………...……....……...VII List of Appendices………………………….………………………..……....…. .. IX Abbreviations...…………………………………………………..……….………....X Abstract...............................................................................…..………….………...XII 1. Introduction……………………………………………………………………….1 1.1 Background information. …………………………………………..…….…...1 1.2 Exploration, number and forms of fish species in Ethiopia…….… ..……......2 1.3 Spatial distribution pattern of Ethiopian fishes…………..…..………..……...6 2. Objectives of the study…………………………………………………..………..9 2.1 General objectives……………..……………………..……………..…….... ..9 2.2 Specific objectives……………...………………..…………………...…...….9 3. Description of the study area……………………………………….…….10 4. Materials and methods…………………………………………………………...15 5. Results and discussion………………..………………………………………….23 5.1 Physical and chemical (abiotic) parameters………....…………………....…23 5.2 Fish species composition of Beles and Gilgel Beles Rivers..………...….......24 5.2.1 Key to Beles and Gilgel Beles River fishes…………….…….…...…......25 5.2.2 Diagnostic and descriptive characteristics of Beles and Gilgel Beles River fishes……………………………..……….…….....…..…..30 III 5.2.3 Species diversity and relative abundance……………………….….……55 5.2.3.1 Species diversity………...……………………………..…….........…55 5.2.3.1.1 Species diversity during wet and dry seasons………...…..….....61 5.2.3.2 Relative abundance of fishes…………………..….……......…....…..63 5.2.3.2.1 Relative abundance of fishes during wet and dry seasons…......66 5.2.2.3 Length frequency distribution of the most dominant species…......…69 5.3 Some biological aspects of the dominant fish species……..…….….….……70 5.3.1 Length-weight relationship………………………….……...……………70 5.3.2 Fulton condition factor (FCF)…………........………………...……...…..73 5.3.3 Reproductive Biology………………..…...………………..…..…………75 5.3.3.1 Sex ratio…………...……..……………………………..…….………75 5.3.3.2 Fecundity………………………………………............…...............…77 6. Conclusions and Recommendations…………………………………………..…80 7. References…………………………………………………………………….…83 8. Appendices…………………………………………………… ………… .…...94 IV LIST OF TABLES Page 1. Fish diversity and endemicity in the six main drainage systems of Ethiopia (Golubtsov and Mina, 2003)………………..…………………….……4 2. Estimated distances from Gilgel Beles at Mender hullet, altitude and coordinates of sampling sites……………………………………………………...…...…15 3. Physical and chemical Parameters of sampling sites (Mean + SD) (O = Oxygen, T = Temperature, S = Secchi depth, Con = Conductivity, RW = River width and RD = River depth)………………………………………………...……..…...23 4. Fish species composition of Beles and Gilgel Beles Rivers……………........…..24 5. Species composition of Beles and Gilgel Beles Rivers (+ = present: - absent)...... 56 6. Comparison of JERBE and present study (+ = present; - = absent).....................58 7. Number of species (N) and diversity indices (H’) for total catch at sampling sites and rivers………………………………………………………………..……59 8. Mean number of species (N) and diversity indices (H’) for fish caught in Beles and Gilgel Beles Rivers.........................................................................................59 9. Number of species (N) and diversity indices (H') for fish caught during wet and dry seasons……………………………………………………….………......61 10. Mean number of fish species (N) and diversity indices (H’) during wet and dry seasons…………………………...……………………………………..……62 11. Total number and weight (kg) of fish specimen caught from Beles and Gilgel Beles Rivers…………………………..…………………………………...…63 12. Index of relative importance (% IRI) for fish species caught during Beles and Gilgel Beles River surveys……………………………………..…64 13. Mean % IRI of the common species in the two rivers…….…....….…..……...65 14. Number and weight (kg) of fishes in the two rivers during wet and dry seasons…………………………………….……………………...………….66 V 15. Mean number and weight (gm) of fishes in the two rivers during wet and dry seasons……………………………………………………..……...…………66 16. Index of relative importance (% IRI) of fishes in the two rivers during wet and dry seasons. ……………………………………………….67 17. Mean % IRI of the common species in the two rivers during Wet and Dry seasons………………………..……………………………...………………68 18. Length-weight relationship of the most dominant species in Beles and Gilgel Beles Rivers…………………………………………...………..………..…..71 19. Mean ± SD Fulton condition factor (FCF) for L. forskalii and L. intermedius in Beles and Gilgel Beles Rivers…………………….....……………………..… 74 20. Mean ± SD Fulton condition factor (FCF) in sex for L. intermedius and L. forskalii……………………………………………………………..……….….……74 21. Mean + SD Fulton condition factor (FCF) for L. intermedius and L. forskalii in Beles and Gilgel Beles Rivers during the two seasons (combined data).…..75 22. Number of males, females and the corresponding sex ratios of fish species of Beles and Gilgel Beles Rivers (data from all sites pooled) ………..…..…....76 23. Mean absolute and relative fecundity of L. intermedius in relation to fork length…………………………………………………. …………….…........78 VI LIST OF FIGURES Page 1. A map showing major drainage basins of Ethiopia (Golubtsov and Mina, 2003). 10 2. Monthly mean maximum and minimum temperature at Mankush and Pawi stations from 2003-2005 (Ethiopian Meteorological Agency, 2005)…..…...…...12 3. Mean monthly rainfall at Mankush and Pawi stations 2003-2005 (Ethiopian Meteorological Agency, 2005)…………………………………………...…...…12 4. Map of Beles and Gilgel Beles Rivers (not scaled) (FDROE, MOWR, 2000)....16 5. Principal measurements of fish (Skelton, 1993)……….……....…...……………18 6. Lateral view of R. loati……………………………….……….………..………. 30 7. A: Lateral view of V.beso; B: Ventral view of mouth region ................………..31 8. A: Lateral view of L. niloticus; B: Ventral view of head region ..........................32 9. A: Lateral view of L. horie; B: Ventral view of head region..................…..……33 10. A: Lateral view of L. coubie; B: Ventral view of head region .................……..34 11. A: Lateral view of L. forskalii; B: Ventral view of head region……………….35 12. A: Lateral view of L. cylindricus; B: Ventral view of head region.....................36 13. A: Lateral view of L. bynni; B: Ventral view of mouth region ..........................37 14. A: Lateral view of L. intermedius; B: Ventral view of mouth region................ 38 15. A: Lateral view of L. nedgia; B: Ventral view of mouth region. ………......….39 16. A: Lateral view of L. degeni; B: Ventral view of mouth region ......... ..............41 17. Dorsal view of C. gariepinus……………………………...………..…...….…..43 18. Dorsal view of H. longifilis…………….………………...………...……………..…44 19. Lateral view of B. bajad………….………………………………….…...…………...45 20. Lateral view of B. docmak……….………………………..……….…………...46 21. A: Lateral view of A. occidentalis; B: Ventral view of mouth region .............. 47 VII 22. A: Lateral view of S. serratus; B: Ventral view of mouth region ......................48 23. A: Lateral view of S. schall; B: Ventral view of mouth region......................... 49 24. Lateral view of H. forskhalii ……………………………..….……………………….50 25. Lateral view of B. macrolepidotus…….…………………….……….…….…….….51 26. Lateral view of B. nurse ………………………………...……….…...………………52 27. Lateral view M. Kannume………………….…..………….………….…….………...53 28. Lateral view O. niloticus………………………….……....……...……………..……54 29. Length frequency distribution of L. intermedius (N=362) and L. forskalii (N=186) in Beles and Gilgel Beles Rivers…...……………...........……….......…69 30. Length – weight relationship for A= L. intermedius and B = L. forskalii in Beles River………………………………………………………..…..……...…....….72